Within your own network it doesn't matter what you use. The important part is that you route the addresses that need to be visible.

Between your peer you will need to use a public address, but in your internal network you should use a private address range. If you are given internet addresses for nodes to be seen on the internet, servers, vpn's etc., then you will need to have these addresses routed within your network, as that's where the internet will be expecting them to be. Your users, core, etc. do not need to have public addresses, as no internet users should want to see them!!